Huffington Post: Hard-to-predict sudden changes to Earth's environment are more worrisome than larger but more gradual impacts of climate change, according a panel of scientists advising the federal government. A 200-page report released Tuesday by the National Academy of Sciences repeatedly warns of potential climate "tipping points" beyond which "major and rapid changes occur." And some of these changes--happening in years instead of centuries--have already begun. They include melting ice in the Arctic Ocean and...